Certain problems arise in the manufacture of components of the aforedescribed nature. These problems are essentially caused by the very small dimensions of the elements concerned and require manufacturing precision. Typical dimensions of electronic circuits of the kind in question are in the order of 0.9.times.0.9.times.0.4 mm and such a circuit will typically weigh 4 mg. The copper filament used in winding the coil has a typical diameter of 0.03 mm including insulation.
In manufacturing such a component, it has earlier been necessary to pre-attach, e.g., a chip to a tool and then wind a coil with the aid of a so-called flyer with one end of the copper filament affixed to a contact point on the chip, and thereafter affix the other end of the copper filament across the next contact point and therewith establish contact across the whole of the circuit, upon completion of the coil winding process. One such method of procedure is described in European Patent Specification 0573469.
A coil that has been manufactured in this traditional manner will have a very non-uniform quality, because the filament, or wire, is taken from an external source and placed adjacent the bobbin centre, which initially has a given shape (thickness), and is wound initially from within and outwards. Consequently, fewer layers of copper filament are obtained where the first end of the filament has passed in towards the centre of the coil and winding has commenced. As a result, the coil will be wider in this region in order to obtain the same number of turns. The corresponding side of the coil then receives more layers and will thus be thicker.
An object of the present invention is to make possible the manufacture of a coil of greater and more uniform quality, by coiling the filament instead of winding the filament with the aid of a flyer, whereby the electronic circuit or circuits is/are kept outside the actual coiling procedure. This more uniform quality is achieved by placing the filament in the centre from the very beginning and then coiling the filament outwards in the tool.
Another object of the invention is to place the chip, etc., in the coil centre hole directly, thereby avoiding the need to fold-in the chip manually.
A further object of the invention is to enable copper filament and chip to be held in place with the aid of sub-pressure, which has been found to be a much simpler and much cheaper solution than the mechanical holders that are otherwise usual.